A secondary battery has been used as high-performance energy source for an electric car, a bulk power storage battery, such as, a battery energy storage system, and small portable electric devices, such as, a cellular phone, a camcorder, and a laptop computer. Thus, a research for reducing weight of a part and electric consumption and improving a secondary battery with reduced size and greater capacity component has been conducted in order to implement the miniaturization and the continuous use of a portable electric device.
For example, a lithium ion battery as a secondary battery can provide greater energy density and greater capacitance per unit area than a nickel-manganese battery or a nickel-cadmium battery. In addition, the lithium ion battery can have reduced self-discharge rate and an extended life. Furthermore, the lithium ion battery does not have a memory effect, and thus, may provide convenience of use and extended life span.
However, as being used as a battery for a new generation electric car, the lithium ion battery may have various problems, such as, a stability problem due to overheating, low energy density, and low power. In order to overcome these problems of the lithium ion battery, the research and development on a post lithium ion battery like a lithium air secondary battery have been actively progressed.
For instance, a lithium sulfur secondary battery can be provided with high energy density, e.g. of about 2500 Wh-kg, which is about 5 times greater than the theoretical energy density of a conventional lithium ion battery. Therefore, the lithium sulfur secondary battery is considered to be a suitable battery for an electric car that requires high capacity and high energy density. However, a polysulfide shuttle phenomenon may occur when a liquid electrolyte is used, thereby causing a self-discharge effect and deteriorating the life span of a lithium sulfur secondary battery. Moreover, safety issue may arise sine the liquid electrolyte is substantially instable at high-temperature during charging and discharging.
In the related arts, Korean Publication Application No. 2013-0123142 discloses a lithium electrode as materials for a secondary battery using lithium, (a lithium metal battery). The lithium electrode comprises a solid super-ionic conductor manufactured with a three-dimensional multi-porous structure; a lithium metal or lithium alloy filled in each of the open pores that constitute the multi-pores; and a collector bound to one side of the solid super-ionic conductor, in which a lithium metal or lithium alloy is filled in each of the pores.
In addition, JP 10-4615339 A has reported a porous solid electrode and an all-solid lithium secondary battery using the same, and has disclosed the electrode for a lithium secondary battery, in which for the electrode for the lithium secondary battery, the electrode is composed of the complex of a porous solid electrolyte exhibiting the lithium-ionic conductivity of 0.5×10−4 S-cm−1 or more and a battery active material that is filled in the pores of the porous solid electrolyte.
Further, Korean Publication Application No. 2013-0073766 has disclosed a cathode for a lithium sulfur secondary battery including a sulfur multi-porous nanocomplex structure and a porous nano conductor, in which i) the sulfur multi-porous nanocomplex structure having the sulfur particles being filled in the pores of a porous conductor having pores and ii) the porous conductor of the same kind without the sulfur particles being filled in the pores are adjacent each other and arranged in a volume ratio of 1:0.1 to 0.9.
JP 2009-094029 A has also disclosed an all-solid lithium secondary battery and an electrode for an all-solid lithium secondary battery, in which for at least one electrode the proportions of a polymer solid electrolyte and inorganic solid electrolyte powder to an electrode mixture including an active material, a conductive composite, a polymer solid electrolyte and an inorganic solid electrolyte powder are less than 50% in a volume fraction.
Moreover, JP 2013-051171 A has disclosed to an electrode body for an all-solid battery and an all-solid battery, in which the electrode body for an all-solid battery includes an electrode layer including an active material particle, a lithium-ionic conductive glass solid electrolyte, and an oxide-based conductor and a solid electrolyte layer including lithium-ionic conductive glass solid electrolyte.
However, even with the above-described known techniques, long-term stability, an inhibition in polysulfide shuttle phenomenon, or high efficiency charge/discharge effect, which is required for an automotive battery system, have not been obtained. In order to solve the above mentioned technical difficulties, the present invention provides a lithium composite as being used as a cathode material, and thus, may provide superior stability and greater efficiency all-solid lithium battery system than the conventional secondary lithium batteries.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.